Transformer system



May 2, 1933I T. MCL. DAVIS 1,907,400

TRANSFORMER SYSTEM Filed July 23, 1927 IN VEN TOR.

ATTORNEY Patented May 2, 1933 UNITED STATES PATEr orifice THOMAS MCL. DAVIS, F WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO VJIRED R'ADIG, INC., 0F NEW', YORK, N. Y., A CORPORATION OF DELAWARE TRANSFORMER SYSTEM Application led July 23,

connected in such amplification circuits.

One of the objects of my invention is to provide a construction of amplifying transformer and a circuit arrangement for such transformer whereby the fine wire windings of the transformer may be protected against destruction.

Another object of my invention is to p rovide a circuit arrangement for an amplifying transformer in which the peimanency of the condition of the transformer is increased by the protection of the line wire windings in the transformer from the action of electroly sis.

Still another object of my invention 'is to provide a transformer system for amplifiers used in connection with electron tubes wherein the primary and secondary windings have an electrode interposed therebetween, which electrode is charged to a higher positive potential than either the primary or secondary windings, with the result that the said primary and secondary windings will both be at cathode potential with respect to the said electrode, and deterioration due to electrolysis will occur in the said electrode and not in the said primary or secondary windings.

My invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawing, wherein:

Figure 1 illustrates an amplifying trans former having its parts arranged in accordance with the principles of my invention with an electrolysis shield disposed between the primary and secondary windings; Fig. 2 shows a modified construction of transformer illustrating the relative arrangement of the electrolysis shield with respect to the primary and secondary windings; Fig. 3 illustrates a modified arrangement of the electrolysis shield with respect to the primary and secondary windings; Fig. 4 illustrates a further modified form of trans- Yformer system showing an arrangement of electrolysis'shield which may be employed;

1927. Serial No. 208,042.

and Figs. 5, 6 and 7 show some of the circuit arrangements in which the amplifying transformer may be employed, with several of the ways in which relatively high potential may be placed upon the electrolysis shield in accordance with my invention.

In electron tube amplification systems it is customary to utilize relatively high potentials for exciting the plate circuits of the electron tubes. The amplifying transformer and other inductances in the amplification circuits may have a comparatively large difference in potential in adjacent or closely spaced parts, and there is a tendency for open lcircuits to occur in the high potential windings.

Investigations with amplifier coupling transformers have proven that the cause for open circuits is generally due to electrolytic action between the high direct current potential of the primary and that of the secondary or other low potential parts. If it were pos'- sible to find a non-leaking insulation medium, under all conditions, this would in itself prevent the action. It has been found, however, that with the use of waxes and other substances common to the art, there will be an electrolytic leakage in a humid atmosphere due to the hygroscopic properties of the insulating medium. i

In the process of this electrolytic action the anode or higher potential winding decomposes at a rate depending upon the leakage current. I have found that this difliculty may be avoided by using a special type of coil in which a third winding or electrode is supplied. This electrode is placed in the leakage path and is maintained at a higher direct current potential than that of either the primary or secondary windings. By this arrangement the transformer windings are both at cathode potential with respect to the third electrode and the deterioration would occur in the third electrode only.

The third electrode is placed in the pat-h of the greatest possible leakage. The loca tion and form of the third electrode is dependent upon the type of coil employed as well as its surrounding dielectric and protection from moisture.

Referring to the drawing, reference character 1 designates the primary winding which is disposed upon the insulating tube 2 and is covered by the insulating tube The electrolysis shield is represented at 4 as wound over the insulating tube 3. An insulating tube member 5 is disposed over thc electrolysis shield 4, and upon this insulating tube 5 is wound the secondary coil 6, the entire assembly bein enclosed by the insulatin tubular mem r 7. The electrolysis shleld 4 which constitutes the third electrode is in the form of an open ended winding of insulated conductive material which may be similar to that of the windings but larger in cross-section. By using similar metals the possibility of galvanic action is eliminated.

As the duration lof effectiveness depends upon the life of the electrode, it is made of wire of relativelyY large size as compared to that of the windings 1 and 6. Inasmuch as the electrolysis shield 4 may actually be destroyed by the electrolytic action the arrangement of the coils may be such as to permit a renewal of this element as it becomes necessar Iii Fig. 2 the primary winding 1 is of the pancake type and is positioned adjacent a similar secondary winding 6. The electrolysis shield is wound in the form of a flat spiral represented at 4 between the windings 1 and 6. The insulatinfr member 7 encloses the windings 1 and 6 as lheretofore explained in connection with Fig. 1.

In Fi 3 I have shown the electrolysis shield 4 isposed in a different relation with respect to the primary and secondary windinUs 1 and 6. In this instance the electrolysis shield 4 is wound upon the outside of the insulating cover member 7, and thereafter the electrol sis shield 4 is covered by means of a protective housing 8.

In Fig. 4 I have shown the primary windin 1 and secondary winding 6 disposed on tu ular member 2, and then concentrically beneath the tubular member 2 the electrolysis shield 4 is disposed, the shield 4 being mounted upon the tubular member 9 which may be mounted directly over the core represented at 10.

In Fig. 5 I have shown the circuit arrangement of an amplification system employing my invention where electron tube 11 has its output circuit 12 coupled with the input circuit 14 of a succeeding stage of amplification including electron tube 15. The amplifying transformer system is designated at 16. The electrolysis shield 4 is shown as disposed between the primary winding 1 and secondary winding 6. In order to impress a higher direct current potential upon the electrolysisI shield 4 than exists in either winding 1 or winding 6, I provide a connection from the positive side of the B battery 17 to the electrolysis shield 4. The primary winding 1 is connected to the positive side of the B battery 17 through the resistance 18. In this way the electrolysis shield 4 serves as an electrode charge to a positive potential higher than that of either the primary winding 1 or the secondary winding 6 so that leakage currents will cause deterioration only in the electrolysis shield 4.

In Fig. 6, I have shown the electrolysis shield 4 provided with a terminal 19 which may extend to a selective terminal at a roltage of higher ositive potential than the positive side of B liattery 17, such as for example, a power tap on a B battery eliminator.

In Fig. 7 I have shown the electrolysis shield 4 connected direct to the positive side of B battery 17 through conductor 20 for imparting to the electrolysis shield 4 a potential higher than potentials existent in coils 1 and 6 by reason of the lower resistance of85 the electrolysis shield 4 due to the large wire size thereof as compared to the fine wire windings in coils 1 and 2.

The transformer system may be im regnated in wax or resin or a combination t ere-(p of for avoiding the penetration of moisture.

I find that moisture penetrates the outer surfaces of the coils first, and once the leakage starts, it generally continues to follow the same path due to the increasing conductance :p of that path by virtue of electrolytic action. In cases where it would not be objectionable from the insulation standpoint, the core itself or even the container and core could be made to serve as the third electrode.

Stray currents which would otherwise tend to electrolytically attack the fine wire windings of the amplifying transformer system are so controlled by the electrolysis shield 4 that the transformer remains substantiallyzgog; permanent. Where the electrolysis shield 4 becomes worn by the continued electrolytie action, it is a simple matter to replace the shield, thus saving the transformer windings. Such replacement is very infrequent by rea- #-110 son of the relatively large size of the third elect-rode and the fact that it may be subjected to deterioration over a substantial period of time without being rapidly consumed.

7hile I have described my invention `in E115 certain of its preferred embodiments, I desire that it is to be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended clai1nsfl2k What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A transformer system comprising primary and secondary windings inductivelv re-f'125 lated to each other and a'member in the form of a winding the individual turns of which being larger in cross-section than the crosssection of the individual turns of said primary and secondary windings and charged` to a positive potential higher than the potentials existing in said primary and secondary windings for confining the leakage path between said windings to a predetermined limit.

2. In a transformer system for electron tube amplifiers, a transformer having primary and secondary windings for coupling the output circuit of one electron tube with the input circuit of a succeeding electron tube, a member disposed adjacent said windings, said member having an open ended conductor of larger cross section than the cross section of the individual turns of said primary and secondary windings and being charged to a positive potential substantially greater than the potentials existing in said windings for providing a definite leakage path from each of said windings to said member and preventingl the action of leakage currents from one winding upon the other winding.

3. An inductance device comprising a plurality of elements of electrically conducting material, one of which is a winding in close proximity to another of said elements, a source of direct current potential applied directly to said other of said element-s and through a resistance to said winding and means for preventing electrolytic corrosion of said winding including said resistance for lowering the potential of said winding with respect to said other element, said means also including a more massive structure of said other element than of said winding whereby it is rendered durably resistive to corrosion.

4. An inductance device comprising a plurality of windings; a source of direct current potential connected directly to one of said windings and through a resistance to a second of said windings, the first said winding being characterized by a relatively greater cross sectional arca of its conductor than that of the second said winding and by having only one connection with said source of potential; and means including said resistance for preventing an electrolytic How of current from the second to the first of said windings.

5. An inductance device comprising primary and secondary wire windings, a conductive shield member composed of an open ended coil of wire of larger gauge than that of the wire in said primary winding, said shield being rendered durably resistive to electrolytic corrosion by its relatively massive structure, and said shield being disposed in the path of possible leakage currents between said windings. and means including suitably differentiated potentials applied to said windings and to said shield member respectively for determining the direction of How of said leakage currents from said shield to said windings.

6. An amplifying transformer for electron tube circuits having primary and secondary windings arranged for coupling the output sion.

THOMAS MCL. DAVIS. 

